Genome engineering technology started since the 1970s and this technology has developed quickly. It is now a more efficient and sturdy tool for genetic perturbations. Genome engineering is a process of altering a genetic layout of an organism in a specific and targeted fashion, and surrounds the techniques or strategies to accomplish the modification process as well. This has enabled researchers to expand our knowledge of what we know about the gene function. The possibilities to alter DNA allows researchers to imitate human diseases in animal models. Hence this can be used for gene therapy and drug development. (Geurts, et al. 2009)
There are currently four major classes of genome editing, zinc finger nucleases (ZFNs), transcription activator-like effectors (TALENs), megaculeases and the latest addition, the clustered regularly interspaced short palindromic repeats (CRISPR)(Mali, et al. 2013). By inducing site-specific DNA double-strand breaks (DSBs), these four technologies can manipulate genetic material. This would result in genome editing through homologous recombination (HR) or non-homologous end joining (NHEJ) (Niu, et al. 2013). Even though they are categorized under the same category; programmable nucleus, the mechanism of each genome editing technologies are different from each other. Generally, specific DNA sequences are targeted by nucleases such as TALENs, meganucleases and ZFNs via protein-DNA interactions (Stranneheim, 2012). The homing endonucleases, also recognized as meganuclease are highly specific according to nature ; its DNA binding domains and nuclease are merged into one sole domain. Whereas, TALENS and ZFNs are nucleases that are artificially engineered with a non-specific nuclease domain of Fok1. Hence, ZFNs and TALENs are more efficient than meganucleases because they are not limited in their capacity to bind to new DNA sequences with specificity.